COronary and MICrocirculatory Measurements in Patients With Aortic Valve Stenosis.

Aortic stenosis (AS) is the most common primary valve disease leading to surgery or catheter intervention in Europe, with a growing prevalence due to the aging population. Severe AS is associated with significant morbidity and mortality and is treated by surgical valve replacement (SAVR) or transcatheter aortic valve implantation (TAVI). However, significant coronary artery disease (CAD) is reported in more than 60% of patients with AS, and this concomitant CAD needs to be correctly assessed because untreated significant CAD is associated with adverse outcomes. Current guidelines recommend intra-coronary pressure measurement using either fractional flow reserve (FFR) or non-hyperemic pressure ratios (NHPR) for the assessment of intermediate coronary artery lesions before revascularization. However, correctly identifying hemodynamically significant coronary stenoses by FFR or NHPR is difficult in patients with AS because of the hypertrophic remodeling related to the valve pathology, which interferes with coronary blood flow in the microcirculation and reduces the accuracy of FFR and NHPR. This has resulted in substantial controversy in this field of coronary artery disease and there is currently no clear guideline for the management of AS patients with concomitant CAD. Recent technological advances now permit the concomitant evaluation of FFR/NHPR and microcirculatory function at the time of cardiac catheterization. Using this technology, we will simultaneously evaluate the hemodynamic significance of coronary stenoses (using FFR and a NHPR - Resting Full cycle Ratio [RFR]) and the microcirculatory function (Index of Microcirculatory Resistance, IMR) in patients with AS and CAD prior to SAVR/TAVI. Eighty patients with AS and intermediate CAD will be included in the study. During routine pre-valve replacement cardiac catheterization, measurement of intermediate CAD lesions (by FFR and RFR) and IMR will be performed using new software. These measures of CAD severity will be compared with a gold standard non-invasive test (single photon emission computed tomography [SPECT]). This will validate the use of RFR and determine if IMR can be used to improve the ischemia prediction of FFR. Subsequently, when these patients undergo a post-intervention (whether SAVR or TAVI) evaluation 6 months after valve replacement, the effect of valve replacement on FFR, RFR and IMR will be determined.